Conventionally, a microcapsule type adhesive for adhering a threaded member such as screw, bolt, nut, and machine screw is well known. Furthermore, it is known that an inorganic filler such as silica, alumina, and calcium carbonate is blended with the microcapsule type adhesive for purposes of efficiently breaking the microcapsule, controlling fluidity of the adhesive, enhancing viscosity of the adhesive and the like. For example, a fastener in which a film of an adhesive composition comprising a monomer with (meth)acryloyl group emulsified into water by a polymer with film-forming ability, an encapsulated organic peroxide with an amino resin as a wall film, and a reducing agent which forms redox with the organic peroxide is formed on a screw portion is known, and the fastener is characterized in that the film is formed by repeatedly applying and drying the adhesive composition several times (Patent Document 1). It is described that, in the adhesive composition, fine powder of silica, alumina or calcium carbonate, potassium titanate fibers, and a glassy or ceramic microballoon may be added as a torque adjusting agent in the amount of 30 weight parts or less with respect to 100 weight parts of the monomer with (meth)acryloyl group. In the example, borosilicate glass with a particle diameter of 40 to 50 μm is used. Furthermore, a method for manufacturing an adhesive is known, the method being characterized in that a mixture comprising predetermined amounts of a monomer with (meth)acryloyl group emulsified into water by a polymer with film-forming ability, an encapsulated organic peroxide, and a reducing agent which forms a redox system with the organic peroxide is agitated in the substantial absence of oxygen (Patent Document 2). It is described that, in the adhesive, talc, silica, alumina or calcium carbonate may be used for imparting a thixotropic property. Furthermore, it is disclosed that, in a method for sealing two abutting metal surfaces, a sealing composition in which at least one of: (a) a polymerizable liquid monomer selected from (meth)acrylate ester monomers; (b) a primary initiator of free-radical polymerization; and (c) a combination of an accelerator/a secondary polymerization initiator are microcapsuled, is used (Patent Document 3). In the example, it is described that silica is used as a thickener.
Besides the inventions described above, inventions in which an inorganic filler such as silica is blended with a microcapsule type adhesive are known. For example, a curable composition obtained by mixing and heating a blend comprising as main components (a) a microcapsule containing one or more kind of organic peroxides as an encapsulated substance, (b) one or more kind of compounds with at least one of polymerizable double bonds on an end or a side chain in the molecule, (c) one or more kind of accelerators which form a redox system with the organic peroxide, and (d) a plastisol, is disclosed (Patent Document 4). In the invention, (d) the plastisol is blended to make the curable composition into a viscoelastic fluid state. The component (a) includes peroxides, hydroperoxides, peresters and peramides, the component (b) includes a compound with (meth)acryloyl group on an end or a side chain in the molecule, and the component (c) includes a conventionally known substance such as amines and sulfimides. Furthermore, it is described that spherical, preferably perfectly spherical, silica powder with a particle diameter of 0.1 to 10 μm may be blended with the curable composition as a non-slipping agent for improving a coefficient of friction. Moreover, a precoat-type adhesive composition for a screw member or the like containing (A) a suspension solution obtained by mixing (1) one or more kind of polymerization accelerators, (2) one or more kind of compounds with at least one of polymerizable double bonds on an end or a side chain in the molecule, (3) one or more kind of acidic substances which exhibit acidity after dissolution into water, and (4) an aqueous binder with emulsifying ability which is water-insolubilized by (3) the acidic substance, and (B) a microcapsule encapsulating one or more kind of polymerization initiators, is disclosed (Patent Document 5). In the invention, it is described that stability of suspension particles is enhanced by further adding a colloidal silica solution to the above suspension solution. Moreover, an aerosol-type spraying adhesive composition which is precoated for locking a screw-type fastening fixture is disclosed, the adhesive composition containing a suspension obtained by suspending a microcapsule in which a resin based adhesive is encapsulated and a fine particulate inorganic filler into a solution prepared by dissolving a curing agent and/or a curing catalyst and a resin based binder into a volatile organic solvent, and a propellant, or the adhesive composition containing a suspension obtained by suspending a microcapsule in which a curing agent and/or a curing catalyst are encapsulated and a fine particulate inorganic filler into a solution prepared by dissolving a resin based adhesive and a resin based binder into a volatile organic solvent, and a propellant, each characterized by being applied in an atomized aerosol spray state (Patent Document 6). In the invention, by adjusting a particle diameter of the microcapsule, a particle diameter of the filler, and viscosity of the adhesive liquid, the adhesive liquid is kept in a stable suspended state even after long term preservation and an adhesive composition which can be sprayed from an aerosol container is obtained. It is described that, as the fine particulate inorganic filler, silica, calcium carbonate, calcium silicate, kaolin, alumina, talc or the like is suitable and the fine particulate inorganic filler has action for increasing the amount and enhancing mechanical strength. Moreover, a microcapsule type adhesive composition containing (A) a microcapsule comprising epoxy resin as a core material and aldehyde-based resin or urea resin as a wall material, (B) an emulsion comprising binder resin with emulsifying ability, (C) a water-soluble or water-dispersible amine-based curing agent, and (D) a hydrolyzed and neutralized product of a copolymer obtained from alkyl vinyl ether and maleic anhydride, or a hydrolyzed and neutralized product of crosslinked alkyldiene of the copolymer obtained from alkyl vinyl ether and maleic anhydride, is disclosed (Patent Document 7). The invention provides an adhesive composition with excellent preservability, no liquid dripping when applied, and no generating uneven thickness when dried. It is described that the adhesive composition can further contain silica, alumina, talc, calcium carbonate, mica, kaolin or the like as a filler.
Although, as described above, various adhesive compositions in which an inorganic filler such as silica is blended with a microcapsule type adhesive are known, there is a problem that, if the compositions are used for precoating a screw portion such as bolt and nut, a shaving of a dried film of the compositions is produced from the screw portion when screwed and the shaving is scattered and stuck to a peripheral portion. When the compositions are used for electronic components, the scattering of the shaving causes failure in operation of a sliding part in the components and of machines such as precision components, generation of noise, and failure in energization in a switch or the like. Therefore, a method for preventing the scattering of the shaving has been studied. For example, a polymerizable sealing composition containing polymerizable poly(meth)acrylate, a polymerization initiator, a polymerization catalyst, a binder composed of a (meth)acrylate ester polymer, and a filler is disclosed, the composition being characterized in that the polymerizable poly(meth)acrylate is encapsulated in a microcapsule with the polymerization initiator, or the polymerization catalyst (Patent Document 8). The polymerizable sealing composition is used for coating a screwing portion of a fastener with threads such as bolt and nut, and the use of the polymerizable sealing composition can prevent a shaving of a dried film of the composition from being produced from a screw portion in a shaving state when screwed. The filler is used for purposes of improving heat resistance and promoting breakage of the microcapsule when the polymerizable sealing composition is applied to a screwing portion of a screw or the like. It is described that the filler includes, for example, an inorganic filler such as silica powder, calcium carbonate, talc, diatomaceous earth and clay, and that the inorganic filler is used in the amount of 10 to 30 weight parts per 100 weight parts of the microcapsule.